The Flame station seemed to be the communications hub for the entire island. It connected the Barracks with the other stations on the Island. It also contained a satellite uplink for communications with the outside world, and controlled the sonar beacon.

This is also what is probably used to connect and communicate between the hatches.

Characters are seen using telephones even though there are no visible over-head telelphone wires. DharmaTel was the telephone network on the island as well.